"Richard W.M. Jones" <rjones@redhat.com> wrote:
Jim Meyering wrote:
What do you think of using this?
isascii (*p) && isalnum (*p)
I'm not sure I'm qualified to say what this does on EBCDIC, but quite likely lots of other code breaks there too anyway. This is nicely self-documenting anyway.
As Daniel suggested, isalnum is locale-sensitive. If there's a locale with an alphabetic byte that is outside the logical a-zA-Z range, yet still within 0..127, then the above expression will give a false-positive for that byte. I've been inclined to stop worrying about EBCDIC for years, but a quick search on the web finds that people are still stuck using it, and do report bugs in ASCII-assuming code. This is why autoconf goes to the trouble of doing this: tr abcdefghijklmnopqrstuvwxyz ABCDEFGHIJKLMNOPQRSTUVWXYZ not this: tr a-z A-Z to convert to upper case.